Concrete Footings and Slabs

An engineer’s inspection of a Waffle Slab Before it is Poured

Join me for an inspection of a waffle slab before it is poured.

Check out our inspection of this waffle slab before it is poured. Give it a thumbs up if you’d like to know the 10 most important things to look for when inspecting a waffle slab.

What are the Components of a Waffle Slab?

I had an enquiry the other day.

“What materials are used to build a waffle foundation?”

The materials used to build are waffle foundation are:

  • Black plastic. This is the damp proof membrane that stops moisture rising out of the ground and into a house.
  • Waffle pods. These are polystyrene blocks used to hold the concrete in place until it cures. The deeper the pods the stiffer the waffle slab.
  • Steel reinforcement bars. Steel reinfrocement bars run in the bottom of the ribs and are the ‘bottom reinforcement’.
  • Steel slab mesh. Steel wires welded into a fabric are placed on top of the waffle pods. These are the top reinforcement of the slab.
  • Temporary formwork. Timber or aluminium formwork makes the sides of the waffle pod slab until the concrete is strong enough to stand up lby itself.

Waffle Slab Inspection with Engineer’s Commentry

Check out this video. Matt Cornell gives a commentary on the aspects of this very same video to help you understand the parts of the waffle slab.

Post a Comment or a Question

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This is not a waffle slab

One reply on “An engineer’s inspection of a Waffle Slab Before it is Poured”

Had a waffle pod slab house built by JG King. on a P class site (loose fill)with 300mm of fill in the front half. Their soil class determination said M class (mildly reactive). After a bathtub leak we had slab heave and they put it down to our bad landscaping (copout). Don’t get fooled with this one its the builders domain to control drainage from the start of build to end, and so set up for drainage. After builder’s attitude of blame-shifting( before we discovered faulty plumbing) I checked the height of the slab and found it to be 173 mm high. which they tried to cover up. But the result was that the edge beams were not founded into natural soil as required to carry over the loose fill.
and an extra 173 mm of fill added to the site so slab sitting on 473 mm fill without any piers. which does not comply with AS 2870. Their response was to have their engineers send a letter to say the slab still complied because they “expected” the edge beam had been deepened. A check revealed that the edge beam which would have had to have been 988 mm deep to be founded 100 mm into the natural ground is only 750 mm. so not even as deep as it should have been if slab was correct height(812 mm) Being a bit suspicious about their “M” class soil rating I had the soil re-tested to find it is H2-D rated, highly reactive, not recommended for waffle pod slab on high fill site, and that was before the height stuff-up.
Are engineers answerable for blatantly signing off on stuff-ups to protect their builder? Who are they answerable to?

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